In the assembly process of electronic component devices (to be referred to as “packages”), a technique is primarily employed that consists of electrically connecting an aluminum electrode of a semiconductor element (to be referred to as a “semiconductor chip”) and the inner lead of a lead frame by thermocompression bonding of a bonding wire between the two. In addition, accompanying the recent market trends of reduced size, lighter weight and higher performance, electronic components are continuing to demonstrate higher levels of integration and multiple pins. Consequently, increasingly complex wire bonding steps are being required more than ever before, and in the case of using a copper lead frame, oxidation of the copper surface is progressing to a greater degree as a result of being exposed to high temperatures of 200° C. to 250° C. for long periods of time.
If a conventional sealing material having superior adhesion to unoxidized copper surfaces is used under such conditions, since there are many cases in which adhesion to copper in various surface states in which oxidation has progressed is inferior, there is the problem of the occurrence of separation at the interface between the sealing resin cured product and the lead frame during demolding after sealing and molding the resin and during solder reflow.
In order to inhibit this separation, since improving adhesion between an insert such as the lead frame and the sealing resin cured product is in opposition to improving mold release of the sealing resin cured product from a molding die, when adhesion with an insert such as the lead frame is improved, mold release from the molding die becomes inferior resulting in the problem of decreased moldability.
Prior to the problem of oxidation of a copper lead frame attributable to higher levels of integration of electronic components, a technique was proposed that consisted of the use of a powder composed of a specific quaternary phosphonium salt as a curing accelerator from the viewpoints of curability and soldering heat resistance (see, for example, Patent Documents 1 and 2). According to this technique, although adhesion and mold release with respect to unoxidized copper were superior, there was the problem of decreased adhesive strength of the sealing resin to an oxidized copper frame.